This is not valid advice, in my opinion. Length times DC resistance per length unit tells you the series resistance a wire will add. A center channel wire under 6 feet long would not cause measurable voltage drop even at 16 ga. But this kind of thinking made Noel Lee a very wealthy man!
That said, upgrading the wire to use better materials and construction may improve your listening quality…but not just heavier gauge OFC. For example, Nordost White Lightning or Purple Flare are light gauge wires, but many reviewers recommend them for clarity, smoothness, and musicality. Spend a few bucks and upgrade all 3 LCRs. Other brands may suit you. Look at Cardas too.